1. Field of the Invention
The present invention relates to hemoglobin combined with a poly(alkylene oxide), which is a novel combination and which is hereinafter referred to as "modified hemoglobin", for as an oxygen carrier in a blood substitute, and to lyophilized preparations containing the modified hemoglobin.
2. Description of the Prior Art
It has been reported that hemoglobin covalently combined with a poly(alkylene oxide) is excellent as an oxygen carrier in a blood substitute because the life time of this modified hemoglobin in the circulation is much longer than that of unmodified hemoglobin itself (see JP Nos. 12308/1981, 206622/1982, U.S. Pat. Nos. 4,301,144 and 4,412,989).
Hemoglobin is a constituent of the living body. However, there are the following problems in the modification of hemoglobin: (1) hemoglobin is denatured during reaction with a poly(alkylene oxide) and (2) the affinity of hemoglobin to oxygen is increased by the chemical modification. Moreover, the stability of the bonding between the hemoglobin and the poly(alkylene oxide) is not stable enough for the modified hemoglobin to be stored for an extended period of time.